Document Detail

Inhibition of nitric oxide synthase with L-NAME does not increase lactate production at rest or during short-term high-intensity exercise in Thoroughbred horses.
MedLine Citation:
PMID:  11519679     Owner:  NLM     Status:  MEDLINE    
The present study was carried out to determine whether inhibition of nitric oxide (NO) synthase promotes anaerobic metabolism in exercising horses, resulting in a significantly increased blood lactate concentration. N(omega)-nitro-L-arginine methyl ester (L-NAME) is a potent inhibitor of NO synthase that has been tested in horses and other species. Two sets of experiments, namely placebo (saline control) and L-NAME (20 mg/kg, i.v.) studies, were carried out on seven healthy, sound, exercise-trained, Thoroughbred horses in random order, 6 to 7 days apart. In both experiments, an incremental exercise protocol was used and data were obtained at rest, during submaximal exercise performed at 8 m/s on a 4.5% uphill grade, and during galloping at 14 m/s on a 4.5% uphill grade--a workload that not only elicited maximal heart rate and induced exercise-induced pulmonary haemorrhage, but also could not be sustained for more than 90 s. Measurements were also made in the recovery period. Mixed-venous blood samples, obtained at matched intervals in the two sets of experiments, were analysed in triplicate for determining the lactate concentration. Following administration of L-NAME, significant bradycardia occurred at rest (27 +/- 1 vs 37 +/- 2 beats/min in the placebo trials; p<0.0001) as well as during submaximal exercise (183 +/- 4 vs 200 +/- 4 beats/min in the placebo trials; p<0.001), but the heart rate increased during galloping at 14 m/s on a 4.5% uphill grade to reach values observed in the placebo trials (215 +/- 2 beats/min) and significant differences were not found. At rest, the mixed-venous blood lactate concentration was similar in the two experiments. With exercise, the mixed-venous blood lactate concentration increased progressively as work intensity increased in both trials, but significant differences were not found between the placebo and the L-NAME experiments during submaximal exercise, near-maximal exercise or recovery. These experiments demonstrated that inhibition of NO synthase in Thoroughbred horses does not promote enhanced anaerobic metabolism at rest or during short-term incremental exercise leading to galloping at maximal heart rate.
M Manohar; T E Goetz; A S Hassan; P Rothenbaum; S Humphrey
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Veterinary research communications     Volume:  25     ISSN:  0165-7380     ISO Abbreviation:  Vet. Res. Commun.     Publication Date:  2001 Aug 
Date Detail:
Created Date:  2001-08-24     Completed Date:  2002-01-30     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8100520     Medline TA:  Vet Res Commun     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  483-94     Citation Subset:  IM    
Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, 61802, USA.
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MeSH Terms
Blood Pressure / drug effects
Endoscopy / veterinary
Heart Rate / drug effects
Horses / physiology*
Lactic Acid / biosynthesis*,  blood
NG-Nitroarginine Methyl Ester / pharmacology*
Nitric Oxide Synthase / antagonists & inhibitors*
Physical Conditioning, Animal / physiology
Physical Exertion / drug effects,  physiology*
Random Allocation
Rest / physiology
Reg. No./Substance:
50-21-5/Lactic Acid; 50903-99-6/NG-Nitroarginine Methyl Ester; EC Oxide Synthase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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